The present invention relates to a polysaccharide which is useful as an ingredient in a variety of foods containing psyllium, which is known to generate a high viscosity when hydrated. In accordance with the present invention, a polysaccharide which can reduce viscosity resulting from hydrated psyllium is provided. In addition, a food additive composition containing the polysaccharide and psyllium is provided. The food additive can be readily incorporated into foods without a loss of beneficial effects of psyllium and without an undesirable increase in the viscosity of the foods. Further, the present invention also provides a food product characterized by its ingredients, which are the psyllium viscosity-reducing polysaccharide and psyllium, and by its excellent handling properties and favorable palatability, and a method of manufacturing the same.
A recent trend of western-style dietary habits in Japan resulted in a continuous reduction in the consumption of dietary fibers. The current daily intake of dietary fibers is as low as about 17 g, which is far lower than the target level of 20 to 25 g prescribed by Ministry of Health and Welfare in Japan. In response to physiological studies directed to the actions of dietary fibers in a human body, the importance of dietary fiber in health care and disease control has been well recognized. Accordingly, various attempts are made to incorporate a dietary fiber into various foods for the purpose of increasing the intake of dietary fibers, which otherwise tends to be deficient.
We focused on psyllium, among dietary fibers, which was reported to have excellent water-retaining capability and swelling ability, as well as various physiological effects such as an intestinal function-controlling effect, blood lipid-controlling effect, hyperglycemia-suppressing effect, and blood cholesterol-reducing effect. Also, psyllium is barely digested and contains few calories, but provides a sense of satiety, and thereby is expected to exact a weight-controlling effect.
Psyllium is a naturally occurring vegetable gum derived from a seed of a plant of Plantago species, such as Plantago Ovata Forskal, which is a kind of plantain cultivated in Rajasthan and Gujarat states in India. Psyllium forms a highly viscous dispersion when hydrated, and it can form a dispersion having the viscosity as high as about 4000 cp (centipoise, determined using a type B viscometer with Rotor No. 3, at 30 rpm and 25xc2x0 C.) for example, even when added at a concentration as low as 1% by weight. When hydrated at 2% by weight, psyllium usually forms a gelatin-like clear gel. When a 1% dispersion is heated to 90xc2x0 C. and then cooled, a hard gel mass can be formed. The viscosity, which is as described above, is several or several ten times greater when compared with other thickening polysaccharides, such as guar gum, locust bean gum, and tara gum, added at the same concentration. In addition, although these thickening polysaccharides exhibit fluidity, even at a high viscosity, psyllium exhibits both high viscosity and high gelling ability.
Accordingly, when psyllium is incorporated into food products, such as beverages, confectioneries, breads, and noodles, in an attempt to obtain physiological effects, such as the intestine function-controlling effect as described above, the psyllium can be swollen during the manufacturing process later than the step of mixing with water due to the physical characteristics described above, thereby resulting in high viscosity. As a result, problems such as difficulties in processing and adverse effects on palatability are experienced, and applications in the field of food processing have been hampered. Therefore, a technique to suppress the onset of the elevated viscosity and gel-forming characteristics in response to the hydration of psyllium is still desired for the purpose of providing an improved handling of psyllium that is to be incorporated into various food products.
Especially, when manufacturing a liquid food to be packed into a sealed container is intended, the manufacturing process requires a step of heat sterilization following the hydration step of psyllium. Therefore, several problems result, such as formation of a hard gel, leading to impossibilities in packing into a container and to difficulties in retaining favorable fluidity or palatability.
A conventional method for suppressing the onset of the elevated viscosity resulting psyllium is disclosed in Japanese Patent Application Laid-Open No. 5-15340, which discloses a method of processing a dietary fiber psyllium in which an agar solution prepared by heating for dissolution is supplemented with psyllium powder, and then solidified by cooling. In this method, although psyllium is fused by means of the coagulating action of agar, thereby achieving a decrease in viscosity, the coagulated psyllium and agar should be used together, preferably as a pulverized solid, and thus a reduction in the gelling ability of the psyllium alone in a hydration system is not achieved. In addition, because the usable form is a pulverized solid including agar, the scope of the applicable food products is necessarily limited.
An object of the present invention is to provide a psyllium viscosity-reducing polysaccharide capable of suppressing the onset of an elevated viscosity and gel-forming characteristics (hereinafter referred to simply as xe2x80x9cviscosityxe2x80x9d) resulting from the hydration of psyllium, without deteriorating the physiological effects naturally associated with the psyllium, such as an intestinal function-controlling effect and the like.
Several attempts were made to achieve the object described above, and it was discovered, unexpectedly, that when a certain polysaccharide, such as a specified starch, is present in a hydration system for psyllium, the onset of elevated viscosity in a psyllium hydrate can be suppressed significantly. A further effort was made to finally identify such polysaccharides, thereby establishing the present invention.
Thus, an aspect of the present invention is to provide a polysaccharide for reducing the viscosity resulting from psyllium (i.e., xe2x80x9ca psyllium viscosity-reducing polysaccharidexe2x80x9d) having a molecular weight of 20,000 or greater and viscosity of an aqueous solution at 2% by weight of 9.0 cp or less (determined using a type B viscometer with Rotor No. 1, at 60 rpm and 25xc2x0 C.). A polysaccharide having these characteristics can reduce the viscosity in a psyllium hydrate system without deteriorating any useful physiological property possessed naturally by psyllium, and without interfering in the manufacturing process or causing any adverse effect on palatability when incorporated into a water containing food.
The psyllium viscosity-reducing polysaccharide according to the present invention preferably is granulated to impart a desirable psyllium viscosity-reducing ability. Such polysaccharides can efficiently prolong the onset of an elevated viscosity upon hydration of psyllium, thus it is advantageously used for the manufacture of a powdered food for preparing a liquid food, such as powdered juice mix or powdered instant soup mix, namely food products which are prepared by dissolving in water, or in hot or boiling water, prior to drinking/eating them. It is preferable that the polysaccharide is granulated to yield 70% by weight or more of the particles being unable to pass through the 140 mesh sieve (140 mesh on), thereby the desirable psyllium viscosity-reducing effect, handling feasibility and solubility of the food product, as well as a preferred dispersion property and bulk density, can be achieved.
In a first aspect of the present invention as above-described, the psyllium viscosity-reducing polysaccharide preferably can be one selected from the group consisting of a modified starch, gum arabic, arabinogalactan, partially decomposed guar gum, pullulan, a dietary fiber, and mixtures thereof, due to the excellent psyllium viscosity-reducing ability thereof.
In particular, the modification method to obtain a modified starch can be, for example, one or more of oxidation, etherification, esterification, and gelatinization.
The polysaccharide particularly preferred in the present invention is selected from the group consisting of oxidized tapioca starch, oxidized potato starch, acid-treated gelatinized potato starch, waxy cornstarch octenyl succinate, acid-treated hydroxypropyl etherified tapioca starch, and mixtures thereof.
Another aspect of the invention is to provide a food additive composition containing psyllium, and the psyllium viscosity-reducing polysaccharide. Since this food additive composition contains psyllium together with the polysaccharide described above, it readily can be incorporated into a food product, especially into a liquid food manufactured in a water-based system, or a food whose manufacturing process involves heating in a hydrated condition. Because the psyllium thus incorporated retains its beneficial physiological effect, the psyllium provides a desirable effect to a consumer of the food comprising the composition.
The invention also provides a food product characterized by its ingredients, namely psyllium and the psyllium viscosity-reducing polysaccharide. Such a food product preferably can be a food whose starting material itself contains water, a food prepared by adding water during its manufacturing process, or a food intended to be prepared or cooked by adding water just before eating, such as noodles, confectioneries, cereals, iced confectioneries, breads, chilled confectioneries, soups, processed sea foods, processed meats, beverages, and dairy foods.
Moreover, another object of the present invention is to provide a liquid food comprising psyllium and the polysaccharide for reducing the viscosity resulting from the psyllium, wherein the polysaccharide has a molecular weight of 20,000 or greater and viscosity of an aqueous solution at 2% by weight of 9.0 cp or less (determined using a type B viscometer with Rotor No. 1, at 60 rpm and 25xc2x0 C.), and is selected from a group of modified starches consisting of etherified starch, esterified starch, and any mixture thereof.
In this aspect of the invention, the onset of an elevated viscosity/gel formation in a psyllium hydrate can be suppressed and a reduction in the viscosity/gelling ability can be achieved, even if the method includes a step of heating, and the physiological effects associated naturally with psyllium, such as an intestinal function-controlling effect, may not be deteriorated. A prominent suppressive effect on the onset of the elevated viscosity/gel formation in a psyllium hydrate can be achieved using the specified polysaccharide as described above (molecular weight: 20,000 or greater; and the viscosity of an aqueous solution at 2% by weight: 9.0 cp or less (determined using a type B viscometer with Rotor No. 1, at 60 rpm and 25xc2x0 C.). However, some of the candidate polysaccharides may not be practical because additional problems arise when the hydration system comprising the polysaccharide and psyllium is heated. Namely, when the hydration system containing such polysaccharide having low viscosity was heated for the purpose of sterilization, gel formation was initiated, then the gel body was separated from the aqueous phase. The gel developed in such a manner cannot be easily broken for dispersion in a homogenous liquid, even if it was thoroughly crushed using a food mill or the like.
The modified starch preferably is selected from the group consisting of acid-treated hydroxypropyl etherified tapioca starch, waxy cornstarch octenyl succinate, and a mixture thereof, which exert desirable effects to suppress the onset of the viscosity/gel formation. In addition, they can suppress the remarkable onset of an elevated viscosity resulting from psyllium upon heating, and can significantly reduce gel strength.
As another aspect of the invention, a method for manufacturing a liquid food is provided, comprising the steps of: (a) preparing an aqueous solution comprising psyllium and at least one modified starch selected from the group consisting of etherified starch, esterified starch, and a mixture thereof, said modified starch having a molecular weight of 20,000 or greater and a viscosity of an aqueous solution at 2% by weight of 9.0 cp or less (determined using a type B viscometer with Rotor No. 1 at 60 rpm and 25xc2x0 C.); (b) packing the solution into a container followed by sealing; and (c) sterilizing the solution by heating any time before, during, or after step (b) is conducted. In this method of manufacturing a liquid food, psyllium preferably can be added after dissolution of the modified starch during the step (a), thereby more efficiently preventing the onset of elevated viscosity/gel formation upon the addition, followed by heating, of the psyllium is accomplished. Moreover, it is preferable in this method to select the modified starch from the group consisting of acid-treated hydroxypropyl etherified tapioca starch, waxy cornstarch octenyl succinate, and a mixture thereof, because a liquid food comprising psyllium can be provided, which has a lower viscosity and gel strength while the physiologically beneficial effects associated naturally with psyllium, such as intestinal function-controlling effect, can be preserved, even if heat sterilization is conducted after preparing the solution which contains psyllium. Thus, in accordance with this aspect of the invention, manufacturing a liquid food which comprises psyllium is enabled, wherein facility in handling and palatability in consumption are both excellent.
Furthermore, another aspect of the present invention is to provide a powdered food for preparing a liquid food comprising psyllium and a psyllium viscosity-reducing polysaccharide, wherein the polysaccharide is granulated, while having a molecular weight of 20,000 or greater and the viscosity of an aqueous solution at 2% by weight of 9.0 cp or less (determined using a type B viscometer with Rotor No. 1, at 60 rpm and 25xc2x0 C.). Because a polysaccharide having such characteristics can exert an efficient psyllium viscosity-reducing effect, it can be added readily to psyllium-containing food products, such as a powdered food for preparing a liquid food (e.g., powdered juice mix or powdered instant soup mix), which are prepared in a water containing system, and the food products which comprise water, such as jelly or liquid beverage, while the physiologically advantageous effects of the psyllium are preserved after preparing the food products. Thus, beneficial effects are imparted to the consumers of these food products.